The goal of this research proposal is to use patient derived cells with defined disease genotypes to identify disrupted molecular pathways through large-scale proteomics and network analysis. Human induced pluripotent stem cells (hiPSC) have revolutionized the ability to study human diseases from patients. It is now possible to obtain fibroblasts from patients suffering from a disease and to reprogram the cells to pluripotent stem cells and then differentiate them into a cell type associated with the disease state. This reverses a long standing limitation for the proteomic study of human diseases which has been the ability to use cells directly from patients with the appropriate disease phenotype and genotype. We will use Rett Syndrome (RTT) as a prototype for autism spectrum disorders (ASD). Here, we will combine vertical (mutant and control cell lines) and horizontal genetics (different mutations in MeCP2) to measure proteomic changes in affected forebrain neuronal and glial cells derived through fibroblasts and hiPSCs. We will use network analysis techniques developed in the previous grant period to identify molecular phenotypic differences using protein-protein interaction and protein expression patterns. Our hypothesis is that this approach will identify specific molecular processes disrupted in RTT and altered upon rescue of the RTT neuronal phenotype, which will lead to insights into other ASD.